General bearing sealing devices include only a single seal, and the seals of two such bearing seal devices are attached to the respective sides of a rolling bearing by fixing the outer peripheral edge of each seal in a seal groove formed in the inner periphery of the outer race of the rolling bearing, with a seal lip or lips of each seal in contact with a seal contact surface formed on the outer periphery of the inner race of the rolling bearing.
Rolling bearings directly exposed to soil, sand and muddy water, such as rolling bearings mounted to agricultural machines use bearing sealing devices each including a first seal fixed to the outer race, and a second seal disposed outwardly of the first seal to prevent the entry of foreign matter. The radially inner portion of the second seal is fixed to the outer periphery of the inner race, and the radially outer portion of the first seal is fixed to the inner periphery of the outer race. By fixing the first and second seals in this way, foreign matter has to move a longer distance until it reaches the interior of the bearings, so that this arrangement ensures higher seal performance.
The below-identified patent document 1 discloses a conventional device sealing a bearing with two seals as described above. This device includes an inner seal fixed in a seal groove of the outer race; an outer seal fixed in a seal groove of the inner race. The inner seal has a plurality of seal lips which are in contact with a cylindrical, seal contact surface formed on the outer periphery of the inner race. The outer seal has also a plurality of seal lips which are in contact with a cylindrical, seal contact surface formed on the inner periphery of the outer race.